1. Field of the Invention
The present invention relates to a control apparatus and to a control method that control an electric oil pump that supplies oil to a power transmission device transmitting a drive force to an axle.
2. Description of Related Art
Japanese Laid-open Patent Application Publication No. 2009-293649 discloses a technique, for use in a vehicle provided with a mechanical oil pump driven by an engine and an electric oil pump driven by a motor, as pumps for supplying oil to a power transmission device (such as a transmission and a start-up friction component) connected to the engine, the technique causing the electric oil pump to be driven during an idle reduction, in which the mechanical oil pump is stopped.
Here, as a drive frequency of the electric oil pump increases, a drive noise decreases. Thus, to decrease a noise level noticed by an occupant, it is desired to set a higher drive frequency.
However, if the drive frequency of the electric oil pump is high, an amount of heat generated in a drive circuit may be large compared to that at a lower drive frequency. Thus, in a situation in which the electric oil pump is continuously used, the drive circuit may be damaged by the heat.
The drive circuit can be prevented from being damaged by the heat when a heat-radiating property of the drive circuit is improved.
However, in a system in which the mechanical oil pump driven by the engine and the electric oil pump are provided, and the mechanical oil pump is mainly used while the electric oil pump is secondarily used, there may be the following problems.
That is, if the heat-radiating property of the drive circuit is improved such that sufficient heat-radiating performance can be obtained even when the electric oil pump is continuously used, cost may increase and the drive circuit may become large. Furthermore, if a lower drive frequency is set to suppress the heat generation amount, the noise may increase.